NAME

SYNOPSIS

DESCRIPTION

Wait for events on the epoll file descriptor epfd for a maximum time of
timeout milliseconds. The memory area pointed to by events will contain
the events that will be available for the caller. Up to maxevents are
returned by epoll_wait(2). The maxevents parameter must be greater
than zero. Specifying a timeout of -1 makes epoll_wait(2) wait
indefinitely, while specifying a timeout equal to zero makes
epoll_wait(2) to return immediately even if no events are available (
return code equal to zero ). The structepoll_event is defined as :
typedef union epoll_data {
void *ptr;
int fd;
__uint32_t u32;
__uint64_t u64;
} epoll_data_t;
struct epoll_event {
__uint32_t events; /* Epoll events */
epoll_data_t data; /* User data variable */
};
The data of each returned structure will contain the same data the user
set with a epoll_ctl(2) (EPOLL_CTL_ADD,EPOLL_CTL_MOD) while the events
member will contain the returned event bit field.

RETURNVALUE

When successful, epoll_wait(2) returns the number of file descriptors
ready for the requested I/O, or zero if no file descriptor became ready
during the requested timeout milliseconds. When an error occurs,
epoll_wait(2) returns -1 and errno is set appropriately.

ERRORS

EBADFepfd is not a valid file descriptor.
EFAULT The memory area pointed to by events is not accessible with
write permissions.
EINTR The call was interrupted by a signal handler before any of the
requested events occurred or the timeout expired.
EINVALepfd is not an epoll file descriptor, or maxevents is less than
or equal to zero.

CONFORMINGTO

epoll_wait(2) is a new API introduced in Linux kernel 2.5.44. The
interface should be finalized by Linux kernel 2.5.66.